Comparison of different extraction methods for polysaccharides from Dendrobium officinale stem.

The purpose of this study was to screen the optimum extraction of polysaccharides (DOP) from Dendrobium officinale stem. Firstly, different methods, including hot water extraction (HWE), cold-pressing (CP), freeze-thawing cold-pressing (FTCP), ultrasonic-assisted hot water extraction (UHWE), microwave-assisted hot water extraction (MHWE) and enzyme-assisted hot water extraction (EHWE), were employed to extract DOP under their respective best parameters. Then, the extraction yield, structure and antioxidant activity of the polysaccharides from different extraction methods were compared under the same condition. The data implied that UHWE and FTCP possessed higher extraction yield than the other extraction methods. Besides, DOPCP and DOPFTCP had higher molecular weight than the other polysaccharide samples. More importantly, DOPFTCP had the highest antioxidant activity. Overall, DOPFTCP exhibit high extraction yield, well-preserved molecular chains and best antioxidant activity, all these indicated FTCP was the most suitable method to extract DOP.